Fluid translating device having expansible chambers

ABSTRACT

A fluid translating device for a pressure fluid system comprising expansible chamber units, and working members therein, so combined and working in unison as to divide fluid from a source for delivery in equal parts to other sources. When the units are of even number the device is bidirectional in that it will divide flow when flow is in one direction in the fluid system or will combine flow when flow in the same system is in the opposite direction. Each unit (e.g., cylinder and piston) has three ports for communicating with a source and two additional ports respectively connected to a port communicating with the expansible chamber of another unit, whereby fluid from a source drives one working member (piston) which itself translates fluid to another source. In a preferred embodiment, two units valve each other, and effective ports are switched as a piston moves through a 90* position.

' United States Patent [191 Shaw et a1.

FLUID TRANSLATING DEVICE HAVING EXPANSIBLE CHAMBERS Inventors: Edwin L. Shaw, Oxnard; Everett H.

Brewer, Thousand Oaks, both of Calif.

Assignee: Abex Corporation, New York, N.Y.

Filed: June 12, 1972 Appl. No.: 261,593

US. Cl. 137/101; 137/111; 137/624.14;

Int. Cl. G05D 11/00; GOlF 3/14 Field of Search 137/567, 101, 111, 624.14; 73/239, 249, 250; 417/225; 91/477; 184/7 References Cited UNITED STATES PATENTS 12/1951 Hjarpe t. 417/225 4/1952 Renick 137/101 5/1957 Hatter 184/7 5/1958- Higgins 184/7 l/l966 Robson et a1 184/7 5] Nov. 4*, 1975 Primary Examiner-William R. Cline Attorney, Agent, or FirmKinzer,,Plyer, Dom & McEachran ABSTRACT A fluid translating device for a pressure fluid system comprising expansible chamber units, and working members therein, so combined and working in unison as to divide fluid from a source for delivery in equal parts to other sources. When the units are of even number the device is bidirectional in that it will divide flow when flow is in one direction in the fluid system or will combine flow when flow in the same system is in the opposite direction. Each unit (e.g., cylinder and piston) has three ports for communicating with a source and two additional ports respectively connected to a port communicating with the expansible chamber of another unit, whereby fluid from a source drives one working member (piston) which itself translates fluid to another source. In a preferred em bodiment, two units valve each other, and effective ports are switched as a piston moves through a 90 position.

29 Claims, 38 igures U.S. Patent Nov. 4, i975 Sheetlof 16 3,916,931

TO/FROM FIRST TO/FRGM TO/FROM SECOND SUB SYSTEM PRESSURE/RETURN SUB SYSTEM I we (1 \6D F|G.l

6A \6B To/FRoM ANOTHER TO/FROM ANOTHER EXPANSIBLE CHAMBER EXPANSIBLE CHAMBER A 24 is 26 235 1B 23 \5 VALVI N6 LANDS FIGJ A INC, TO/FROM VALVING TO/FROM vA LVING AN NULUS AN NULLJS ANNULUS A 30 5 6D 8 CYLINDER] CYLl NDER 2 US. Patent Nov. 4, 1975 Sheet2of16 3,916,931

CYL 2 FIGZC U.S. Patent Nov .4,1 975 Sheet4ofi6 3,916,931

MAGNETIC INLET PICK-UP FIGS l To QD ELECTRIC E R COUNTER MAGNETIC OUTLET PICK-UP FROM SYSTEM TO SUB SYSTEM m J D f g) 5 FIG.4

TO SYSTEM RETURN FROM SUB SYSTEM RI SYSTEM I P2 SYSTEM R2 PUMP Pl PUMP She et 5 of 16 3,916,931

US. Patent Nov. 4, 1975 m 86 m l US. Patent Nov. '4, 1975 Sheet 6 of 16 U.S. Patent Nov. 4, 1975 Sheet7of 16 3,916,931-

US. Patent Nov. 4, 1975 Sheet8of 16 3,916,931

U.S. Patent Nov. 4, 1975 Sheet 10 of 16 3,916,931

l FIRST PORT FOURTH FIFTH PORT To I T l 'l' FIG.7I' SECOND THIRD PORT V32 PORT FIFTH FIRST FOURTH PORT PORT PORT o 4 TO 173 US. Patent Nov. 4, 1975 Sheet 12 of 16 3,916,931

CYL I S B k h/CYL4 SLAVE P I STO N US. Patent Nov. 4, 1975 Sheet 13 of 16 3,916,931

CYL8

{ @Li B /CYL3 CYL7 U.S. Patent Nov. 4, 1975 Sheet 14 of 16 3,916,931 7 SUPPLY RETURN U.S. Patent Nov. 4, 1975 Sheet 15 bf 16 4, 1975 ;Sheet 16 of 16 U.S. Patent Nov.

VALVING EDGES VALVING EDGE FGR3TO4 flsmaom B t E. r VALVING EDGE FOR 2TO5 VALVING EDGE F1619 vAEwNG EDGEs VALVING EDGE STO-iORS FLUID TRANSLATING DEVICE HAVING EXPANSIBLE CHAMBERS This invention relates to self-valving devices which may be used for a variety of applications. These include, but are not limited to, such devices as flow dividers/combiners, transfer units, intensifiers, hydraulic circuit breakers, and flow meters. Aircraft serve a good example of where such devices may be employed; however, in addition to aircraft, other types of vehicles and- /or stationary hydraulic systems may use these devices for similar purposes.

Aircraft embody controls which require equal and concurrent movement; thrust reverser flaps on jet engines, so-called leading edge devices on wings, lift flaps, and spoilers are examples. Additionally, transfer units may be employed for interconnecting hydraulic power from one system to another without interchange of systems fluids. Intensifiers may be used to increase operating pressures in order to obtain smaller sized actuators where space and aerodynamic considerations are a factor. Hydraulic circuit breakers may be used to protect portions of a hydraulic system. Deintensifiers may be used where high pressure low flow is converted to low pressure high flow; a fuel transfer unit driven by an aircraft hydraulic system is an example. The use of flow meters is obvious, both for aircraft and other purposes. The present invention may be applied to all of these.

Fluid divider/combiner or fluid proportioning devices are known such as US. Pat. No. 2,593,185 where a main stream of entrant fluid is proportioned within internal chambers and delivered to a pair of outlets, utilizing proportional valve means. There, however, pressure responsiveness is a very limiting factor, and one object of the present invention is to develop a flow divider/combiner able to divide a main stream of fluid equally between two branches or outlets without in any amounts of fluid to each of the outlet systems. Should the obstruction cause the pressure in one of the outlet systems to reach that of the supply pressure, the unit will stall thus positioning each of the actuators in the outlet system in identical positions. An additional feature of the device is that when in the combining mode,

should something restrict the supply to the divider/- combiner from one of the subsystems, the unit will operate at a speed which is governed by that of the lowest pressure of the two supply sub-systems. Should jamming of an actuator occur, supply to the divider/combiner would be stopped to one side of the divider/combiner. The unit would stall, thus again positioning both actuators in identical positions.

It is obvious that such things as fan thrust reverser flaps, lift flaps, leading edge devices, or speed brakes, and similarly configured control devices operating out of parallel (not synchronized) can cause an aircraft to go into an unbalanced control mode. It imperative that such control systems be operated to prevent an imbalance from occurring, otherwise loss of control of aircraft could occur.

In the chemical industry there are many instances where a source of fluid is to be divided and delivered in equal proportions to mixing chambers of reactor vessels, or it maybe desirable to mix fluids in proportions. The present invention is useful in thisregard as well.

It can be seen from the foregoing that a need exists for a flow. divider/combiner. Other applications are obvious for transfer units, -intensifiers/de-intensifiers, and

hyraulic circuit breakers. It may be stated categorically illustration, show preferred embodiments of the present invention and the principles thereof. Other embodiments of the invention employing the same or equivalent principles may be used and structural changes may be made as desired by those schooled in the art without departing from the present invention.

In the drawings:

FIGS. 1, 1A and 1B are sectional views of a cylinder with the piston thereof in three different positions;

FIGS. 2 through 2E are schematic views showingthe sequencing of a two-cylinder bidirectional flow, device in the dividing mode, operating in accordance: with the present invention; I

FIG. 2F presents a summary of the acting as a flow divider;

FIG. 3 shows the two cylinder form of a flow meter; I

FIG. 4 shows the two cylinder device modified as a circuit breaker;

FIG. 5 shows the two cylinder device as unit;

FIG. 6 is a diagrammatic view showing a six cylinder unit operating in accordance with the present invention;

FIGS. 7-71 are diagrammatic views, and FIG. 7.] is a chart, showing operation of a four cylinder arrangement in accordance with the present invention;

FIGS. 8, 9, 9A and 10 are schematic views of another four cylinder arrangement;

FIG. 11 is a schematicview of an eight cylinder arrangement;

device of FIG. 2

device modified to the a transfer FIG. 12 is a side elevation of a commercial form of GENERAL STATEMENT; GENERAL RULES The devices of the present invention comprisean even number of expansible chamber units having working members therein moving repetitiously between a first and second position. During movement the working member in each unit alternately expands and contracts two expansible chambers, such that as one chamber is being expanded the other or opposite one is being contracted.

In the specific embodiments, the expansible chamber units are cylinders and each working member is a reciprocal piston. When at one limit position of an operating cycle defined as 360, which may be taken as the or 360 position, the piston completely contracts a first expansible chamber and completely expands a second expansible chamber; and as the piston moves through a 90 position to a 180 position, the first chamber undergoes expansion as the second chamer is being contracted, the first chamber being completely expanded and the second chamber being completely contracted as the working member attains the 180 position. When the piston reverses, moving from the 180 position through a 270 position back to zero, expansion and contraction are reversed.

TWO CYLINDER ARRANGEMENT AND ADDITIONAL GENERAL RULES (FREE RUNNING PAIR) As an introduction to the cyclically operable expansion chamber devices of the present invention, consideration shall first be given to the construction of a cylinder and related piston used for translating fluid between a main source and two branches. FIG. 1 is a schematic illustration of a cylinder incorporating a piston or spool 16, the piston being located in a first position at one extremity of the cylinder; FIG. 1A shows the same piston in its intermediate position, the center or 90 position; FIG. 1B shows the same piston in the other extremity or 180 position.

The cylinder has two expansible end chambers 21 and 22 having ports P affording ingress and egress of fluid under pressure. Thus the piston will be moved as by the admission of pressurized fluid to the left-hand port P, FIG. 1, shifting the piston to its right-hand limit position shown in FIG. 1B.

The heads of the piston are afforded by lands 16A and 16BB at the remote ends of the piston. Additionally, the piston includes two intermediate lands 16C and 16D with grooves or reduced areas therebetween, the arrangement being such as to define three interior passages or chambers 20, 23 and 24. The medial one of the passages is at all times in communication with a first port 26 which may be connected to the main stream of fluid S.

Passages 23 and 24 are related respectively to second and third ports 23B and 24A. As will be explained, fluid derived from the main source is effectively directed to ports 23B and 24A in the sequence of operation. However, the reverse may prevail in that fluid may be combined for return to the source S.

The medial passage 20 at all times is in communication with one or the other of a pair of ports 20-1 and 20-2 allowing direct flow of fluid therebetween in either position. Four lands are shown, but three lands may also be used, as will be described. Regardless, the land edges are such that while the medial passage 20 constantly communicates with the first port 26, neither of the second and third ports is ever in direct communication with the first port 26.

Thus, the basic unit is preferably a cylinder presenting two opposed expansible chambers, one at each end, and a working member in the form of a piston is disposed therein. The expansible chambers are separated by the end lands on the piston. The expansible chamber unit has a first port 26 which may be connected to a first source of fluid S, and second and third ports 24A, 23B which may be connected to second and third sources of fluid A and B; but these three ports may be used in many different modes. Each expansible chamber unit has a fourth port and a fifth port 20-1; 20-2. Porting and valving are critical. The first, second and third ports of one cylinder always communicate with sources as shown in FIGS. 1A and 1B; and the fourth and fifth ports of one unit respectively communicate with the expansible chambers of another unit as shown in FIG. 1B as will shortly be described for a device consisting of two cylinders so connected, FIG. 2, where the ports are shown by progressive numbers one through five in circles for each cylinder.

Thus, the invention assumes an even number of expansible chamber units, at least a pair, each unit having first, second and third ports (which may be connected to fluid sources); each unit has a working member (piston) for contracting the expansible chambers and translating fluid to another unit; each unit further having a fourth port to be connected to an expansible chamber of another unit and a fifth port to be connected to an expansible chamber of another unit. There are internal passage means in the units and valve means on the working members for alternately in each unit of a basic pair a. establishing connection of the fourth port with the first port and the fifth port with the second port when the working member is one side of center, the or 270 position of the piston; and

b. establishing connection of the fourth port with the third port and the fifth port with the first port when the working member is at the other side of the center position.

Said connections are further characterized in that as a pair of working members alternately assume different positions two expansible chambers are always valved to a first port and an alternate one of the second and third I ports.

Thus referring to FIG. 2, Cylinder 1 and Cylinder 2 are associated to divide flow or to combine flow. It will be noted that chambers 21 and 22 and passages 20, 23 and 24 of Cylinder 2, FIG. 2, bear the same reference characters as the corresponding parts of the cylinder shown in FIGS. 1 and 1A. Identical chambers incorporated in Cylinder 1 are identified by a 30 series of reference characters. This allows fluid flow to be easily traced.

The starting condition, FIG. 2, is characterized as a random position of the pistons, but is shown as one where each piston is at the extreme left-hand position of the related cylinder. The starting condition can be any position of the pistons within their respective cylinder bores, inasmuch as the first fluid pulse, being a very small amount standing alone, is of no moment especially since the fluid translating device shown in FIG. 2, will be operating over an indefinite period of times when in use to translate a relatively large quantity of fluid between the sources (S on one hand and A and B on the other). This is equally true of the other fluid translating units disclosed herein. (A and B may be assumed as representing hydraulic motors, each to receive an equal volume of operating liquid).

With further reference to FIG. 2, the streamof supply fluid to be divided or equalized is delivered to passages 20 and 30 of the cylinders through the respective first ports, one. The source fluid from S introduced to passage 30, Cylinder 1, thus flows from the first port to the fourth port and through related passage 30-1 to the left-hand expansion chamber 21 of Cylinder 2, noting that valving land 16D .of Cylinder] blocks the other line of potentialtransfer 30-2; Fluid underpressure delivered to chamber 20 of Cylinder 2 only;has theeffect of holding the piston of Cylinder l in the'left-hand extreme position shown; valving land 16D of Cylinder 2 blocks flow to passage 20 2 and port five of Cylinder 2.

The first shift (see FIG. 2A) is therefore characterized by internal passage of Cylinder 1 servicing the working member or piston of Cylinder 2 in that working fluid under pressure from the source S prevails in chamber 21 of Cylinder 2, driving the piston thereof from left to right resulting in the quantity of fluid in the expansible end chamber 22 of Cylinder 2 being translated to port five and passage 33 of Cylinder 1 and from thence out port three of Cylinder 1 to actuator (source) B. Thus, the lands on the piston of Cylinder l valve ports one and four to an expansible chamber of Cylinder 2, while valving the other expansible chamber of Cylinder 2 to ports five and three of Cylinder 1, resulting in delivery of fluid to actuator B.

The cylinder assembly is now in the course of being reset, FIG. 2A, and it should be noted at this point there is no real pause in operation, which is to say the working members begin constant motion in that as one is midway between extreme positions (90 or 270) it valves the next unit the working member of which starts its shift in the typical circumstance. FIG. 2F charts the sequence of flow division.

Thus, referring to FIGS. 2A and 2B, the interior valving means or lands of the piston of Cylinder l are so positioned that passage 30 and expansible chamber 21 are connected until the piston of cylinder 1 reaches its mid position or 90 'position. At this time thej piston of Cylinder 2 has reached its rightmost position, FIG. 213. Re ferring to FIGS. 2B and 2C, it can be seen that the piston of Cylinder l valves passage 30 from chamber 21 to chamber 22 and chamber 21 is connected to passage 34. The piston of Cylinder 1 continues to travel to the right, FIG. 2B, while the piston of Cylinder 12 has been reversed and it commences to travel to the left to the position shown in FIG. 2C. Referring to FIGS. 2C and 2D, it can be seen that the piston of Cylinder 2 switches the valving to Cylinder 1, FIG. 2C; the piston of Cylinder 1 is then reversed and it commences to travel to the left and the pistons reach the positions as shown in FIG. 2D. Referring to FIGS. 2D and 2E, it can be seen that the piston of Cylinder 1 has switched the yalving to Cylinder 2. The piston of Cylinder 2 commencesto travel to the right while the piston of Cylinder completes its stroke to the left until the positions shown in FIG. 2E are reached. These are the same positions as shown in FIG. 2A. The device has completed one cycle, and this process continues as long as pressure is supplied to the unit and the pressure in ports A and B do not exceed the supply pressure at S.

The process described occurs in reverse when the unit is placed in the combining mode.

The unit must combine or divide accurately as examination will reveal that one end of each piston is ported to one of the A or B ports. As the piston reciprocates, it accepts or delivers first a pulse to one of the ports (A or B) and then to the other port;

To attain bidirectional flow, essential in certain aircraft controls, an even number of units must be utilized. We have determined this, and in fact the rule is tested by the fact that an odd number of units will di- 6 vide flow from a main into separate branches, or will combine flow from two branches for delivery to a main source, but will not do both in the sense of accommodating either forward or reverse flow.

The arrangement of FIG. 2 conforms to the general rule in that each cylinder (even number of cylinders) has five essential ports, aside from the openings associated with the expansible chambers thereof, for translating fluid between the device and the system in which it is installed. Thus, in the first position, FIG. 2, the passage means and valving means presented by the configured pistons, for each unit, connect the first (source) and fourth ports, (the latter in turn being connected at all times to the expansible chamber of another unit) and connect the second (source) port and fifth ports (the latter in turn being connected to the expansible chamber of another unit). Further in the second position for each working member (FIGS. 2A and 28) connections are switched in each unit (and were switched at mid-position of each piston) so that only the first and fifth ports are connected whilst only the third and fourth ports are connected. Consequently, in the even numbered working arrangement of cylinders, a first source port of one unit is alternatively valved by its piston to the fourth and fifth ports of that unit, and the second and third (source) ports of that unit are alternatively valved to the fourth and fifth ports thereof. The fourth and fifth ports are connected to diverse expansible chambers. Thereforethe first port of one unit is always connected to an expansible chamber of another unit, but the second and third (branch) ports thereof are only alternately connected to an expansible chamber of another unit; and since the two expansible chambers of one unit are respectively connected to the fourth and fifth ports of another unit, it follows that for two successive shifts (one piston, then the other) the fourth and fifth ports of two units (even number) are receiving two unit volumes (2X5) while translating half to A branch and half to B branch.

The device, FIG. 2, therefore works in reverse for if A and B are at a pressure higher than S it can be seen that B pressure entering port two of Cylinder 2, FIG. 2, transfers to port five thereof and from thence to expansible chamber 31 causing-jthe piston therein to shift to the right, transfening fluid from chamber 32 to ports four and one of Cylinder 2, returning B to S. The piston of Cylinder I eventually occupies the position shown in FIG. 2C and in moving to, that position valved its port three (A source) to charriber 21 of Cylinder 2 moving the piston of Cylinder 2 tothe right delivering fluid in chamber 22 to the communicated ports five and one of Cylinder l, returning A to S. "In two shifts, sources A and B are combined to produce confluence at S. The piston of Cylinder 2 is now in the position shown in FIG. 2E, moving toward the position shown in FIG. 2B. High pressure at B of Cylinder 1 and B of Cylinder 2 is without effect, but high pressure at A of Cylinder 2, port 3, FIG. 2C is communicated to port four associated therewith and is transferred to the right hand expansible chamber of Cylinder l the piston of which is translated to the left delivering fluid to communicated ports five and one of Cylinder 2, and as it moves through mid-position ports two and five of Cylinder 1 are connected, transferring source B (working fluid) to the right-hand expansible chamber of Cylinder 2. Now, the left-hand expansible chamber of Cylinder 2 is contracted forcing fluid therein to port four of Cylinder l which was communicated to port one thereof (S) when 

1. A cyclically operable fluid translating device comprising an even number of expansible chamber units, at least a pair, each having a pair of opposed expansible chambers and each unit including a working member repetitiously movable between first and second positions to alternately expand and contract the expansible chambers related thereto, delivery of fluid under pressure from one of the units to a contracted expansible chamber of another unit driving the related working member of the other unit from one position to the other, each unit having first, second and third ports, a fourth port of each unit connected to an expansible chamber of another unit and a fifth port of each unit connected to another expansible chamber of another unit, internal fluid passage means in said units, valving means on each working member combined with said passage means for alternately in each unit a. establishing connection of the fourth port with the first port and the fifth port with the second port when the working member is in the first position, and b. establishing connection of the fourth port with the third port and the fifth port with the first port when the working member is in the second position, and the working member of one unit valving the contracted chamber of a second unit paired therewith to a source of fluid pressure prevailing at one of the first three ports of said one unit, and vice versa, so that one working member of the pair constantly lags the other.
 2. A device according to claim 1 wherein each unit comprises a cylinder and each working member is a piston.
 3. A device according to claim 2 wherein the expansible chambers in each cylinder are defined by the end walls of the cylinder and lands at the ends of the piston, and wherein the valve means are presented by land edges on the pistons with reduced areas between the land edges defining said internal passages.
 4. A device according to claim 3 wherein the ports communicate with the reduced areas of each piston.
 5. A device according to claim 1 wherein the passage means, ports and valving means associated with each unit are so located that when one working member is midway between positions said connections are switched.
 6. A device according to claim 5 wherein the paired units are series and reverse connected one to the other, series connected in that the fourth and fifth ports of a first paired unit are connected to the expansible chambers of a second paired unit such that the right port is connected to the right chamber and the left port is connected to the left chamber, and reverse connected in that the fourth and fifth ports of the second unit are connected to the expansible chambers of the first unit such that the right port is connected to the left chamber and the left port is connected to the right chamber.
 7. A device according to claim 5 wherein each unit is in the form of a cylinder and each working member is a piston.
 8. A device according to claim 7 wherein the expansible chambers in each cylinder are defined by the end walls of the cylinder and lands at the ends of the piston, and wherein the valve means are presented by intermediate lands on the pistons with reduced areas between the piston lands defining said internal passages.
 9. A device according to claim 1 comprising four of said units, a fourth port of a first unit being connected to an expansible chamber of each of a second and third unit and a fifth port of said first unit being connected to the two remaining expansible chambers of said second and third units, fourth and fifth ports of said second unit being connected to the expansible chambers of said first unit, and fourth and fifth ports of said third unit being connected to the expansible chambers of a fourth unit.
 10. A device according to claim 9 including two additional units each having a pair of expansible chambers and a working member therein but not having any of the named ports, a fourth port of the fourth unit being connected to an expansible chamber of each of the fifth and sixth units, and a fifth port of the fourth unit being connected to the remaining expansible chambers of the fifth and sixth units, whereby the fifth and sixth units are slaved to the fourth unit.
 11. A device according to claim 1 wherein the working members travel 180* in moving from one position to the other, and wherein the working member in the first of a pair of units in passing the 90* position valves the contracted chamber of the paired unit to a source of fluid pressure prevailing at one of the first three ports of the first unit, and vice versa, so that one working member of the pair constantly lags the other by approximately 90*.
 12. A device according to claim 11 consisting of two units.
 13. Two devices according to claim 12 with the two working members of one device respectively joined to the two working members of the other device in combination as a transfer apparatus.
 14. A device according to claim 12 wherein the second and third ports of one unit are each connected to a system source with the first port thereof connected to a sub-system source; and wherein the second and third ports of the second unit are connected to the sub-system source while the first port thereof is connected to the system source thereby affording a circuit breaker between the system and sub-system.
 15. A device according to claim 12 in which the first port of each unit is connected to a main source of fluid and in which the second and third ports of each unit are combined to reconstitute the main source thereby affording a device having flow meter capability.
 16. A device according to claim 11 comprising four of said units, a fourth port of a first unit being connected to an expansible chamber of each of a second and third unit, a fifth port of said first unit being connected to the two reamining expansible chambers of said second and third units, fourth and fifth ports of said second unit being connected to the expansible chambers of said first unit, and fourth and fifth ports of said third unit being connected to the expansible chambers of a fourth unit.
 17. A device according to claim 16 including two additional units each having a working member and a pair of expansible chambers but not having any of the named ports, a fourth port of the fourth unit being connected to an expansible chamber of each of the fifth and sixth units, and a fifth port of the fourth unit being connected to the remaining expansible chambers of the fifth and sixth units, whereby the fifth and sixth units are slaves of the fourth unit.
 18. A device according to claim 1 in which each working member as it passes mid-position valves the ports and passages of its unit to the passages and ports of another unit, and in which the connections are such that an expansible chamber is always interposed between one of the first three named ports of one unit and those of another.
 19. A device according to claim 18 in which each unit is a cylinder and each working member is a piston, the valving means comprising four land edges on each piston spaced inward from the ends of the piston and spaced from each other, the spaces between land edges constituting internal passages.
 20. A device according to claim 18 in which the valve means, ports and internal passages are such that an expansible chamber never communicates simultaneously with two of the first three ports.
 21. A device according to claim 20 consisting of an even multiple of two units, the ports, passages and valving means being connected so that fluid from a first source delivered to the first port may be distributed in equal amounts to the second and third ports when there is higher pressure at the first port, or fluid at higher pressure in the second and third ports may be combined for return to the first port.
 22. A device according to claim 20 wherein the pistons traverse 180* in moving from oNe position to the other, and wherein the piston in the first of a pair of units in passing midposition valves the contracted chamber of the paired unit to a source of fluid pressure prevailing at one of the first three ports of the first unit, and vice versa, so that one piston of the pair constantly lags the other by approximately 90*.
 23. A device according to claim 22 including an even multiple of two units.
 24. A device according to claim 22 wherein the fourth and fifth ports of one unit are branched, each to service the expansible chambers of two other units in the first and second positions of the working member of said one unit.
 25. A cyclically operable fluid translating device for a pressure fluid system comprising an even number of expansible chamber units, at least four in number, each unit of which translates fluid under pressure between a first source of fluid and second and third sources of fluid, each unit having a pair of opposed expansible chambers, a working member in each unit repetitiously movable through 180* between first and second positions to alternately expand and contract the expansible chambers related thereto, delivery of fluid under pressure from one of the sources to a contracted expansible chamber driving the related working member from one position to the other, each unit having first, second and third ports for translating fluid between the system and the device, each unit having a fourth port connected to an expansible chamber of another unit and a fifth port connected to another expansible chamber of another unit, internal fluid passage means in said units, valving means on each working member combined with said passage means for alternately in each unit. a. establishing connection of the fourth port with the first port and the fifth port with the second port when the working member is in the first position and b. establishing connection of the fourth port with the third port and the fifth port with the first port when the working member is in the second position; and, for each set of four units, the working member of one unit passing midposition valving the contracted chamber of a second unit paired therewith to a source of fluid pressure prevailing at one of the first three ports of said one unit, and vice versa, so that one working member of the pair constantly lags the other by approximately 90*.
 26. A device according to claim 25 consisting of four units.
 27. A device according to claim 25 consisting of eight units.
 28. A cyclically operable fluid translating device comprising an even number of expansible chamber units, at least a pair, each in the form of a cylinder presenting a pair of opposed expansible chambers, each cylinder having a working member in the form of a piston repetitiously movable between first and second positions within the cylinder to alternately expand and contract the expansible chambers related thereto, delivery of fluid under pressure from one cylinder to a contracted expansible chamber of another cylinder driving the related piston of the other cylinder from one position to the other, each cylinder having first, second and third ports, each cylinder having a fourth port connected to an expansible chamber of another cylinder and each cylinder having a fifth port connected to another expansible chamber of another cylinder, internal fluid passage means in said cylinders, and valving means including at least four land edges spaced from one another on each piston and related to said passage means for alternately in each cylinder a. establishing connection of the fourth port with the first port and the fifth port with the second port when the piston is in the first position, and b. establishing connection of the fourth port with the third port and the fifth port with the first port when the piston is in the second position, and the piston of one unit valving the contracted chamber of a second unit paired therewith to a source of fluid prEssure prevailing at one of the first three ports of said one unit, and vice versa, so that one piston of the pair constantly lags the other.
 29. A device according to claim 28, wherein the pistons traverse 180* in moving from one position to the other, and wherein the piston in the first of a pair of units in passing midposition valves the contracted chamber of the paired unit, and vice versa, so that one piston of the pair constantly lags the other by approximately 90*. 